Hitherto, in a case of controlling an AC rotating machine, in order to supply an electric current in an appropriate phase corresponding to a rotational position of a rotor, a position sensor such as an encoder, a resolver, and a Hall element has been necessary. However, in the case of using such position sensor, there has been a problem in terms of price, reliability of the sensor, or the inconvenience of wiring.
Therefore, in order to solve such problem, there has been proposed a control device for controlling the AC rotating machine by estimating the rotational position of the rotor without using the position sensor.
Specific examples of such control device for an AC rotating machine in the related art include a control device in which a rotational speed of the AC rotating machine is estimated by an adaptive observer based on an induced voltage of the AC rotating machine, and the estimated rotational speed is integrated by an integrator to estimate the rotational position (see, for example, Patent Literature 1).
Another example is a control device in which a difference in inductance in components on arbitrary two rotational axes of an AC rotating machine that is electrically salient, which results from saliency that is generated in a case where high-frequency voltages are applied on the two rotational axes, is used to estimate the rotational position (see, for example, Patent Literature 2).
Still another example is a control device in which a difference in inductance, which results from magnetic saturation that occurs in a case where high-frequency voltages are applied on arbitrary two rotational axes of an AC rotating machine, is used to estimate the rotational position (see, for example, Patent Literature 3).